I have a 16 gig 4 enough room for me I'm always changing and music on my iphone though so I never get it full enough and unload all my pictures off my phone. The 4S does look sexy though maybe I'll get lucky and find me a 4S like I found my 4 lol

itunes for iphone big one for me
Another big one battery life, my iphone will last at least 8-10 hours easily with constant texting and ipod usage.
You can easily find a dock for an iphone for speaking player if you want.

I have some of the usual ones like Pandora, eBay, the flashlight, a movie app, and then a couple of workout apps for the gym as well as for swimming. I also have the turbo scan and that is pretty convenient. Works better than I thought it would.